Internal combustion engines, such as the engines employing the known Otto or Diesel cycles, are widely and commonly utilized in vehicles destined for the movement of both persons and of goods, such as passenger, haulage and freight vehicles, including lorries and locomotives. In summary, such engines utilize a fuel having a high hydrocarbon content, such as fossil fuels and/or those originating from renewable sources, to transform the thermal energy from the burning of the fuel into kinetic energy.
The construction of an internal combustion engine is well known and consists, basically, of a piston moving within the interior of a cylinder associated with a crankshaft. On the upper side of the piston there is provided a combustion chamber comprising, among other elements such as spark plugs and/or injection nozzles, at least one intake valve and one exhaust valve. The piston, in turn, generally comprises three rings in contact with the cylinder liner, the upper two rings, that is to say those most proximal to the head of the piston whereat is realized the compression of the combustion gases in the chamber, have the function of ensuring the sealing of the mixture and preventing the escape both of the mixture and of the combustion gases to the interior of the block and, by virtue thereof, they are generally denominated “compression rings”. The third ring, normally located below the two compression rings, has the objective of removing or “scraping” the oil film when the piston descends to prevent the burning of the oil and, in this manner, to moreover reduce the emission of gases. This ring is generally denominated “scraper ring”.
The components and operation of an internal combustion engine both of the Otto cycle and of the Diesel cycle are of common knowledge to those versed in the art, for which reason greater explanations are unnecessary in the present descriptive memorandum.
There exists today a growing concern in respect of the reduction in the emissions of gases produced by internal combustion engines, responsible for a large part of the release of CO2 into the atmosphere. Climate change is one of the most relevant current environmental challenges, having possibly grave consequences. This problem is being caused by the intensification of the greenhouse effect which, in turn, is related to the increase of the concentration in the atmosphere of greenhouse gases (GGs), among them carbon dioxide.
With the objective of minimizing the emission into the environment of harmful gases, such as carbon monoxide (CO), hydrocarbon gases (HCs), nitrogen oxides (NOx), together with particulate materials and/or other GGs, a series of technologies has been incorporated into internal combustion engines in recent years. The reduction in emissions of gases is related, among other factors, to the increase in the thermal performance of engines and, consequently, the reduction in the specific consumption of fuel.
In this sense, technologies such as electronic injection, the catalyst, and particulate matter filters are, today, very widespread and employed in an almost obligatory manner in all internal combustion engines. Other more recent technologies, such as the direct injection of fuel, the common rail for engines utilizing the Diesel cycle, and the utilization on a greater scale of technologies known for a long time, such as mechanical compressors or turbocompressors, are also becoming associated with the objective of increasing energy efficiency and complying with increasingly rigid emission regulations.
As a consequence, combustion engines are developing greater power per volume of displacement of the piston within the cylinder, commonly referred to as specific power output. The performance of an Otto cycle combustion engine in the decade of the 1980s attained, on average, 50 HP/l, and today it may easily attain in excess of 100 HP/l. This means that the combustion pressure within the interior of the cylinders has considerably increased, this also meaning that combustion engines are working under greater mechanical stresses, faster rotation and higher combustion temperature. In this manner, the components thereof must likewise be dimensioned to support these harsher operating conditions in order both to ensure the reliability of the assembly and to maintain the expected working life, today estimated as being approximately 300 000 km for Otto cycle engines in motorcars.
This greater operational stress is translated, likewise, into a greater stress suffered by the components, inter alia the piston and the rings associated with the piston. With the greater degree of compression, combustion pressure, temperature and rotation, the rings also exercise greater pressure upon the piston and upon the walls of the cylinder, likewise leading to greater wear or fatigue of the rings which may increase the play existing between the ring and the cylinder and, in this manner, causing problems related with the wear of the cylinder liner and/or of the piston itself, oil leakage, increase in fuel and/or oil consumption and, even, the rupture of the ring.
The present invention has the objective of overcoming these and other drawbacks encountered in the state of the art.